High-sensitivity Fabry–Perot interferometer temperature sensor probe based on liquid crystal and the Vernier effect

A novel high-sensitivity Fabry–Perot (FP) interferometer temperature sensor based on liquid crystals (LCs) and the Vernier effect is proposed and demonstrated in this Letter. This sensor is prepared by inserting two cleaved single-mode fibers into a section of a capillary tube to generate an FP cavity. The cavity is filled with LCs, which induces a Vernier effect due to the birefringence of LCs. The refractive indices of the ordinary and extraordinary light have different responses to the temperature changes. As a result, the temperature sensitivity is significantly improved by detecting the peak shifts of a periodic envelope. The experimental results show that the proposed sensor can provide a high-temperature sensitivity of 19.55 nm/°C. This sensor offers key features and advantages of the Fabry–Perot interferometer, including low cost and good fringe visibility. Furthermore, such a sensor probe can meet different requirements of temperature sensing in various application areas by using different kinds of LCs.